High molecular weight polymers of acrylamide have found use over the years as flocculants for settling industrial slurries and removing suspended matter from municipal or process water. To be as effective as possible, these polymers should be water-soluble and have a high molecular weight.
One major problem which has been plaguing the industry for many years is the difficulty with which recovery of these high molecular weight polymers in a dry state is achieved. They are normally prepared as very viscous, aqueous gells which must be dried before transportation of the polymers is economical. Drying, however, usually tends to deleteriously alter the properties of the polymers to the extent that water-insolubles form therein and the molecular weight tends to decrease. The reduction in molecular weight is particularly bothersome because the effectiveness of these polymers depends proportionally upon the molecular weight thereof.
U.S. Pat. No. 3,714,136 describes one method of drying and recovering these polymers wherein the gels are cut into fragments and dried while suspended in a gas stream at 20.degree. C. to 100.degree. C. for 5-60 minutes. The gel may be dusted with sodium sulfate or frozen prior to cutting.
While the polymers produced according to this prior art process are excellent overall, they tend to exhibit a loss in viscosity, and consequently molecular weight, after treatment and, as mentioned above, since it is advantageous to achieve the highest molecular weight possible, there exists an opportunity to improve on said process or develop another, wherein drying would not result in a reduction of molecular weight.